This preliminary study shall develop a primate model for pituitary transplantation. This project shall evaluate the feasability of maintaining hormonally-active autologous pituitary tissue within the third ventricle of hypophysectomized male rhesus monkeys and study neuroendocrine relationships with respect to feedback communication and the psychochemistry of behavior. Cerebrospinal fluid (CSF) and blood concentrations of LH-RH, LH, FSH, prolactin, testosterone and cortisol shall be determined before and after transplantation of the animals' own pituitary tissue in hollow fiber units into his third ventircle. CSF shall be sampled via an indwelling fourth ventricular cannula attached to a subcutaneous Ommaya reservoir thus preserving the blood-brain barrier. The adequacy of these implants shall be verified by demonstrating preservation of diurnal rhythms, maintenance of blood steroid hormone levels, inhibition of prolactin secretion and the lack of behavioral depression. Furthermore, LH-RH and ACTH stimulation tests will assess the reserve potential of the implanted pituitary tissue. Correlations between the functional adequacy of the pituitary implant and the degree of behavioral alterations in feeding, sleeping, social interaciion and psychomotor activity may provide insight into psychoendocrine regulation leading to subsequent investigations of other hormonal systems. The validation of this model would facilitate not only future psychoendocrine investigations of deficiency states but would also enable the study of behavioral aberrations associated with hypersecreting pituitary tumors or pharmacological stimulation. This model could potentially be employed for the development of drugs which inhibit the hypersecretion of pituitary adenomas. Retrieval of this implanted tissue within hollow fiber units would offer the possibility of assessing cytological effects of drugs on pituitary adenoma cells. Neurotransmitter and cyclic nucleotide determination of simultaneously obtained CSF samples may reveal neurotransmitter-hormonal interactions that may affect behavior.